%0 Journal Article %J ECOLOGICAL INDICATORS %D 2016 %T Evaluating ecosystem-level anthropogenic impacts in a stressed transitional environment: The case of the Seine estuary %A Samuele Tecchio %A Chaalali, Aurélie %A Raoux, Aurore %A Rius, Armonie Tous %A Lequesne, Justine %A Girardin, Valerie %A Géraldine Lassalle %A Cachera, Marie %A Riou, P %A Lobry, Jeremy %A Dauvin, Jean-Claude %A Nathalie Niquil %X

During 2002-2005, a new container terminal in the commercial harbour of Le Havre, named "Port2000", was built on the northern flank of the Seine estuary, northern France. This extension is already known to have modified the estuary current and sediment dynamics, as well as reducing biomass of the suprabenthos assemblage, for the whole downstream part of the system. However, studies on other biotic communities were largely inconclusive, and an ecosystem-wide analysis was still lacking. Here, we performed a before/after study of ecosystem dynamics of the different habitats of the Seine estuary, using a Linear Inverse Modelling technique (LIM-MCMC) to estimate all flows occurring in the food web. Ecological Network Analysis indices were calculated, summarising ecosystem functioning traits and giving indications about the habitat health status. Results showed that the southern flank (FS, Fosse Sud) exhibits all characteristics to be considered as the least stressed habitat of the estuary: system activity and functional specialisation of flows were stable between periods, ecosystem recycling processes and detrital dynamics were also stable; an increase in trophic specialisation (decrease in system omnivory) was the only change confirming a general ecological succession. The northern flank (FN, Fosse Nord), where the actual terminal was built, showed a food web with increased importance of lower trophic levels (increased detritivory and carbon recycling), increased stability and flow efficiency, but possibly regressed to a previous step in ecological succession. In the central navigation channel (CH), patterns of network indices were overall inconclusive and the general image is one of a constantly shifting food web, a condition possibly caused by the year-round dredging activities. The functioning of the Seine estuary especially of FN and FS - seems to have been modified by the combination of harbour construction and the related mitigation measures. Network indices partially captured this combination of changes and, although not fully operational yet, they are promising tools to comply with the European Union mandate of defining ecosystem health status. (c) 2015 Elsevier Ltd. All rights reserved.

%B ECOLOGICAL INDICATORS %V 61 %P 833-845 %8 02/2016 %G eng %R {10.1016/j.ecolind.2015.10.036} %0 Journal Article %J Marine Ecology Progress Series %D 2014 %T Diversity structure of phytoplankton communities and primary productivity in a temperate epicontinental sea %A Napoléon, C %A Fiant, Liliane %A Raimbault, V %A Riou, P %A Pascal Claquin %K English Channel %K Phytoplankton diversity %K primary production %K Productivity %X The dynamics of the phytoplankton assemblage, the physical, chemical and biological parameters, and primary productivity and production were monitored in the central English Channel along a transect between Ouistreham and Portsmouth from January to December 2010. The spatial patterns of the phytoplankton assemblage were controlled by the hydrological characteristics of the water masses, and the annual structure of the phytoplankton assemblage was characteristic of the central English Channel and was controlled by seasonality. The spring bloom was dominated by a single species, Chaetoceros socialis, and associated with low microphytoplankton evenness and Shannon-Wiener indices, whereas the evenness index was high from late spring to winter and associated with the proliferation of pico- and nanophytoplankton cells. We identified 2 species responsible for harmful algal blooms, Phaeocystis globosa, which dominated the community in the northern part of the Seine Bay in May, and Lepidodinium chlorophorum, which dominated the community near the French coast in September. We examined the relationship between microphytoplankton diversity and maximum primary production and productivity. We found a negative parabolic relationship between the diversity indices (evenness and Shannon-Wiener) and maximum primary production, and a positive parabolic relationship between the number of taxa (richness) and maximum primary production. However, we found no relationship between maximum productivity and the evenness or richness indices. High levels of productivity were measured during the increasing abundance of pico and nanophytoplankton cells, highlighting the importance of taking the dominant functional group into account, rather than the degree of diversity, when explaining the level of productivity. %B Marine Ecology Progress Series %V 505 %P 49-64 %G eng